Electric field deflection of molecules with large amplitude motions

Abstract

The Stark effect is derived for several plausible models for molecules such as XeF₆ and IF₇ which are believed to show pseudorotation or other large‐amplitude internal motion. These results are related to the behavior of these molecules in electric‐field‐deflection molecular beam experiments. The absence of focusing of XeF₆ is compatible with an effective dipole moment of distorted XeF₆ of up to 1.2 D for free pseudorotation but only 0.2 D if pseudorotation is restricted by a potential barrier with C_4v orientation 770 cm⁻¹ above C_3v. Additional examples are treated for XeF₆ as well as models appropriate to the MX₇ molecules.